More Information

Additional Information

Afrosoricidatenrecs and golden moles

Facebook

Twitter

By Phil Myers

Almost all Mesozoic mammals were insectivorous. Insects are by far the largest group of organisms, both in terms of number of species and in biomass. They are marvelously diverse in habit and morphology. They provide a rich resource for anything that eats them, and their diversity alone suggests that their predators might exhibit similar variety. And so it is. Many mammals, including members of almost all orders, sometimes feed on insects. Members of one order, the Insectivora, feed almost entirely on invertebrates, especially insects. The Insectivora includes such groups as shrews, moles, hedgehogs, and tenrecs; these groups include around 375 species arranged in six living families. Tree shrews and elephant shrews have also sometimes been placed in this order; now, however, they are now classified separately (orders Scandentia and Macroscelidea, respectively). To complicate matters, recent research (Murphy et al., 2001) suggests that tenrecs and golden moles also do not belong in this group; rather, they should be classified with other African groups such as hyraxes, elephants, sea cows, aardvarks, and elephant shrews (the "Afrotheria"). For now, however, we leave them with the Insectivora.

What traits characterize members of the Insectivora? Most insectivores are small; shrews, for example, are among the smallest mammals. Most rely more on their senses of hearing, smell, and touch than on vision. Some shrews can echolocate. The part of the brain that houses the sense of smell is especially well developed. The ear region of insectivores lacks an ossified bulla. The tympanic membrane is attached to a bony tympanic ring, and the middle ear may be partially enclosed by processes from adjacent bones. The jugal is reduced or may be absent, and the zygomatic arch is sometimes incomplete. The cheek teeth of many are dilambdodont, and even those with more derived molariform teeth tend to have cusps that can easily be identified according to the tribosphenic pattern. The incisors of some Insectivora are enlarged (but they are reduced in others), and the canines also vary considerably in morphology. The eyes are usually very small, the feet are plantigrade and have five digits, and neither the hallux or pollex is opposable.

Many of the traits used to define Insectivora are probably primitive for mammals. Whether the order is a natural (monophyletic) group is still open to question.

Members of the order are found through much of the world. They are missing from Australia and all but the northernmost part of South America. Most species eat invertebrates.

Contributors

Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

Disclaimer:
The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.